Chemical supercharging of racing engines is well known in the art. Nitrous oxide (N.sub.2 O) is a non-flamable liquid/gas used for such chemical supercharging which when introduced into the combustion chamber of an engine breaks down into its components of nitrogen and oxygen. The free oxygen is then available to oxidize additional fuel ("enrichment fuel") that is supplied to the engine and mixed with the oxygen resulting in a large increase in power. N.sub.2 O injection or charging is usually performed only at critical periods of a race to provide a sudden burst of power since the amount of N.sub.2 O injected is difficult to meter and the use of N.sub.2 O can be hazardous if too much N.sub.2 O is injected.
N.sub.2 O charging or injecting systems usually consist of a cylinder or container holding a supply of liquid N.sub.2 O under pressure, typically 900 psi. The N.sub.2 O supply is connected by a conduit to a solenoid actuated valve at the carburetor of the engine. The solenoid actuator is operated by the driver from within the vehicle at the instant that a sudden burst of power is required. The N.sub.2 O supply container is usually quite small due to weight and space limitations in racing vehicles. This present several problems: the pressure in the small container drops quickly once the solenoid actuated valve is opened and thus affects the amount of N.sub.2 O injected. Since an improper mixture of oxygen and fuel will actually decrease performance, N.sub.2 O injection can only last a few seconds.
The actual amount of N.sub.2 O which should be injected is a function of engine speed (RPM) and if too little N.sub.2 O is injected, the performance increase is limited. Moreover, if too much N.sub.2 O is injected, the engine will be seriously damaged.
Several systems have been proposed for controlling and/or automating N.sub.2 O injection. U.S. Pat. No. 4,494,488 to Wheatley discloses a "Fuel Charging System for High Performance Vehicles" which includes a supply cylinder of pressurized liquid N.sub.2 O connected by an outlet conduit to the vehicle engine. A second cylinder of nitrogen gas under a considerably higher pressure is connected to the N.sub.2 O cylinder through a pressure regulator. The nitrogen gas maintains a high pressure blanket over the N.sub.2 O to force the N.sub.2 O into the engine at a relatively constant and sustained rate. This results in an additional several seconds during which N.sub.2 O injection may be performed.
U.S. Pat. No. 4,683,843 to Norcia et al discloses a "Nitrous Oxide Fuel Injection Safety System" which includes a container of pressurized N.sub.2 O supplied to the engine through a spray bar. The supply line is also connected to a vent tube having a normally open solenoid valve communicating with a one-way low pressure actuated check valve to prevent excess buildup of N.sub.2 O in the engine. A pair of pressure actuated electrical switches are connected to and actuated by pressure of oil and fuel to stop N.sub.2 O injection when there is insufficient fuel to mix with the N.sub.2 O and to prevent N.sub.2 O injection when RPM is too low.
All of the known systems for injecting N.sub.2 O have one common disadvantage. N.sub.2 O is injected in a predetermined amount for a predetermined time only. These systems do not control the amount of N.sub.2 O injection over time, but rather control the amount of N.sub.2 O injection at a specific time. N.sub.2 O injection is still limited to a brief moment of increased power rather than a continuous span of increasing power.
Moreover, it is known in the art that during N.sub.2 O and enrichment fuel injection, ignition timing should be retarded by 4.degree.-10.degree.. However, only a few systems include provisions for adjusting ignition timing during N.sub.2 O injection.
Electronically controlled fuel injection systems have been widely used in normal gasolene and diesel powered engines. One such system is sold by Haltech, Inc. of Garland, Tex. The Haltech.TM. F3 electronic fuel injection system includes sensors for air temperature, engine temperature, throttle position, engine rpm and manifold vacuum and a programmable controller so that the amount of fuel applied to combustion chambers is metered in steps according to information gathered by the sensors. Specifically, this system allows programming of 64 different vacuum/pressure adjustments to map fuel delivery over the range of engine speeds. It is only recently, however, that this technology has been applied to N.sub.2 O fuel injection systems.
Nitrous Oxide Systems of Cypress, Calif. has combined features of electronic fuel injection technology with N.sub.2 O injection systems to control N.sub.2 O boost according to throttle position and temperature and to "ramp" N.sub.2 O injection for a more even boost when N.sub.2 O injection is activated.
To date, however, these electronically controlled N.sub.2 O injection systems operate in a relatively static manner, requiring the user to pre-program the system with a personal computer according to certain parameters which will be followed by the system during activation of N.sub.2 O injection.
Recently, Jacobs Electronics of Midland, Tex. has introduced the "Nitrous Mastermind" (NMM) system. This system allows the user to present the rpm at which N.sub.2 O injection begins and at which N.sub.2 O injection reaches 100%. The NMM system begins N.sub.2 O injection at 40-50% and increases injection to 100% over a straight line proportional to the selected engine speeds. The system also includes several safety features such as an automatic shut-off when fuel pressure falls and/or rpm drops. The NMM system also includes an ignition timing retard adjustment which retards ignition timing 4.degree.-10.degree. during N.sub.2 O injection.
The NMM system does not, however, account for throttle position as a factor in considering the amount of N.sub.2 O injection. It does not allow the adjustment of offset or slope in plotting the N.sub.2 O injection curve. In fact, the NMM system does not plot an injection curve but uses a straight line "in direct proportion to the engine rpm".